Session 4: Safety

Learning Objectives

By the end of this session, you will:

1. Understand the key risks associated with operating a biogas plant.

2. Know the safety precautions to prevent hazards.

3. Be aware of the built-in safety features of the CREATIVenergie system.

4. Have good operational habits to ensure safe and effective use.

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Introduction

Like electricity, bottled gas, and wood fires, biogas can be dangerous if not handled with care. By understanding the risks and following the precautions in this session, you can use biogas safely and effectively.

Fig. 14 Overview of the key safety topics in this session: fire and explosion risks, asphyxiation, toxic gas (H₂S), disease risk, keeping others safe, the EAT daily checklist, and safe stove use.

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Main Risks and Mitigations

🔥 Fire or Explosion Risk

Biogas contains methane, which is highly flammable and explosive under certain conditions.

Precaution	Requirement
Distance from buildings	At least 3 m
Exclusion zone	3 m — no ignition sources
No smoking / fires / electrical equipment	Within 5 m of the digester
Metal tools	Avoid near the plant (spark risk)

😮 Asphyxiation Risk

Biogas can displace oxygen, creating a risk of suffocation.

• Keep the digester outside and well ventilated.

• Do not cover the inlet or outlet with plastic sheeting.

• Install a 1 m fenced exclusion zone to prevent access by children and animals.

☠️ Toxic Gas Risk (H₂S)

Biogas contains small amounts of hydrogen sulfide (H₂S), which is toxic and corrosive to metals.

• Ensure good ventilation around the plant.

• Never enter the digester — even if recently emptied. Gases linger inside.

• Use a H₂S filter (steel wool works as a cheap option) in the pipe before the stove. Replace monthly.

🦠 Disease Risk

The slurry contains bacteria that may carry disease.

• Avoid direct contact with digester contents.

• Use gloves when loading dung.

• Wash hands thoroughly after working with the system.

• Protect cuts and scratches.

• Keep children away from the plant.

Danger

Under no circumstances should you enter the digester. This is highly dangerous — risk of gas poisoning (H₂S), asphyxiation from lack of oxygen, and infection from slurry. People have died from entering digesters.

👥 Keeping Others Safe

Once built, make sure others are not harmed:

1. Cover the inlet and outlet — they are deep and people could fall in and drown.

2. Put a fence around the digester.

3. Cover the digester bag to prevent damage and puncturing.

4. Check valves operate correctly regularly.

5. Ensure the cookstove is in good repair and not leaking.

6. If you detect a leak (digester depressurising or rotten egg smell), get it fixed immediately.

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⚠️ Safety Zone Diagram — click each zone

Each coloured ring represents a different safety requirement around the digester.

👆 Click a zone to see its rules.

🔍 Spot the Hazards — click each marker to reveal the risk

Six hazards are hidden in this scene. Click the orange circles to find them.

Found: 0 / 6

👆 Click any pulsing marker on the diagram above to reveal the hazard.

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Safety Features of the CREATIVenergie System

Feature	Purpose
Biogas Plant Cover	Protects against physical damage and UV exposure
Main Gas Valve	Quick gas shutoff — must be shut off at night and between each use
Bubbler	Prevents flame flashback from reaching the digester
Pressure Release	Excess slurry overflows through inlet/outlet at high pressure — prevents dangerous over-pressurisation
Inlet/Outlet Covers	Prevents people and animals falling in

Fig. 15 Key safety components of the CREATIVenergie system and the correct procedure for safe stove use.

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Daily Safe Operation: The EAT Acronym

To ensure safe operation, remember EAT:

• E — Establish a 1 m exclusion zone around the plant

• A — Assess the system regularly for damage or leaks

• T — Turn off the gas valve after use

🧠 EAT — Daily Safety Checklist

E

Establish

Fence off a 1 m exclusion zone — no children or animals

A

Assess

Check regularly for damage, leaks, or rotten-egg smell

T

Turn Off

Shut the gas valve at night and after every single use

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🔍 Suspected Gas Leak? Follow these steps

Click each step as you complete it. If you find a leak, follow the action below.

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Safe Use of a Gas Stove

For those new to gas cooking:

1. Light a match first, then turn on the gas.

2. Ensure the flame ignites properly.

3. Adjust to a blue, steady flame — no smell or excessive noise.

4. Turn the gas off after cooking.

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🎯 Practice: Identify the Hazards

⚠️ Click on the Hazards

Six situations are shown below. Click the ones you think are hazardous — then check your answers.

Check My Answers

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Session 4 Quiz

Fill in Q1. What is the three-letter safety acronym taught in this session?

Hint: it relates to what you should do and avoid with your digester.

Number Q2. What is the minimum safe distance (in metres) between a biogas digester and any building?

MC Q3. What does H₂S (hydrogen sulfide) smell like, and what makes it dangerous?

Smells sweet; causes headaches only Smells like rotten eggs; toxic and corrosive to metals No smell; purely a fire hazard Smells like bleach; destroys crops

True / False Q4. The correct procedure when lighting a biogas stove is to turn on the gas valve first, then bring the match.

True False

MC Q5. What is the purpose of the bubbler in the CREATIVenergie system?

It heats the gas before use It removes water vapour from the gas It prevents flame flashback from reaching the digester It measures gas pressure

MC Q6. When should the main gas valve be shut off?

Only when a leak is detected Once per week as a maintenance routine At night and between each use Only when filling the digester

Check My Answers

Submit your score to receive credit for this session:

Submit Score via Google Forms →

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Key Reminders

• Always maintain a 1 m exclusion zone around the digester.

• Turn off the gas valve after cooking every time.

• Regularly inspect the system for damage.

• Never enter the digester for any reason.

Next: Session 5: Digestate & Fertiliser